EP1518433A1

EP1518433A1 - Location sevice support for distributed bts architecture

Info

Publication number: EP1518433A1
Application number: EP02755448A
Authority: EP
Inventors: Arto Jantti; Timo Nasakkala
Original assignee: Nokia Oyj; Nokia Inc
Current assignee: Nokia Oyj; Nokia Inc
Priority date: 2002-06-28
Filing date: 2002-06-28
Publication date: 2005-03-30
Also published as: WO2004004399A1; AU2002321714A1; CN1550117A; CN101365245A; CN100423605C; US20040258100A1

Abstract

There is disclosed, in a communication system comprising a receiver and a plurality of sub-receivers, wherein signals received at each sub-receiver are forwarded to the receiver, a method for determining at which one of the plurality of sub-receivers a signal received at the receiver is received from, comprising: allocating a time delay to each sub-receiver; delaying a signal received at each sub-receiver by the corresponding time delay; and determining the presence of a received signal in a time window associated with each time delay, wherein a signal received in a time window associated with a particular time delay is determined to have been received by the corresponding sub-receiver.

Description

LCJCCAATTIIOOlNj SEVICE SUPPORT FOR DISTIRBUTED BTS ARCHITECTURE

Field of tine Invention

The present invention relates to communication systems in

I whic ;ransceι Iver is as Msoci ,a ited w th multiple remote transceivers, for transmitting and receiving a signal associated! with that transceiver. The invention is

I particularly but not exclusively concerned with a mobile communication system in which a donor base transceiver station is associated with a plurality of remote head units. Background! to the Invention

It s an II object of the present invention to provide a solution to one or more of the above-stated problems.

Summcfry of the Invention

According to the present invention there is provided, in a comm nicat Lon system comprising a receiver and a plurality of sub-reiceivers, wherein signals received at each sub- receiver are i forwarded to the receiver, a method for determining at which one of the plurality of sub-receivers a signa¹ ceived at the receiver is received from, comprising allocating a time delay to each sub-receiver; de! aMing a signal received at each sub-receiver by the correspondlng time delay; andt determining the presence of a received slignal in a time window associated with each time delay , wherein a signal received in a time window associated with a particular time delay is determined to have been received by the corresponding sub-receiver.

The communication system may be a cellular communication system, ea :ch sub-receiver being associated with a sub-cell of a cell associated with the receiver. The identijfication of the sub-receiver at which a signal is

illustrates an example of a location determination using a preferred embodiment of the present .

remote head units 56a-56d of Figure 2 may alternatively be In terms of implementation of the rake receiver, the remote head units 56a to 56d, in an indoor radio system, are within a limited distance from the BTS, for example 3 kilometres As siich the whole width of the normal search window is not li eliy to e used. Because the distance between the remote hedds and the BTS is known, the search window can be short

The geographical ocation information of each of the remote head units 56a-56d is stored in the system during the inatallaticn phase. As discussed further hereinbelow, based on the known delay and the known remote head location information, the location of the mobile station can be estim ted, The system compensates for ^'the artificial delays introduced in order to determine the remote head unit, so that the mobile station location estimate gives accurate resulps . Where the implementation of the interface between the remote head jinits and thei BTS is an IF or an RF interface , the use of a SAW filter reduces receiver sensitivity. However this is ncj>t a degenerating factor, ; because the users, i.e. mobile staitions,' are close to the remote head units . The optical delay line may be ! used to Ii!mple 'ment the artificial delay only where the optical interconnection between the remote head units and uhe BTS is [quite long, of the order of hundreds of metres or a kilometre or greater. However this

station tiansmisslion, and to this base station reception.

Together with the identification of the remote head unit receiving : the signal, as discussed hereinabove, this information is used to calculate the position of the mobile station. !

In a pract!leal implementation, more than one of the remote head units 56a-56d will receive a signal from the mobile station As such, the BTS will successfully detect a received signal from more than one remote head station. As d scussed above, the present, invention allows the remote head station at! which signal was received to be identified Such receipt of a signal may occur at multiple i remote head units The furt 2r adaptation of this technique in ! order to provide an curate determination of the locat ion oiif the mobile station preferably uses a technique such as round trip time (RTT) .

Referring bo Figure 4, each delay window 62, 64 and 66 assoσiated with the respective remote head units can also be consdjdered to be RTT windows. Although in this particular embodiment an RTT technique is used, location of the mobile station may be determined using various other techniques, such as cell-ID, or Idle Period Downlink-Observed Time

Di ference of Arrival (IPDL-OTDOA)

Referring no Figure 5, there is further illustrated a system arrangement! of an indoor radio • system according to a preferred implementation of the present invention.

!

Block 100 represents a wideband optical unit (WOU) including wideband optical modules (two of which 130 and 132 are shown in , Figure 5) . The wideband optical module 130 has four connections to respective remote head units 126a 126d via optical connections 128a-128d. The wideband optical module

i i h d i 12'6d These delay elements introduce delays into the respective received signal lines¹ in order to identify the remote head unit at which a 'given signal is received. Thus received aignals on optical ilines 128a-128d are received in the optical module 130 at respective delay elements 152a- 152d. Delay elements delay respective signals, before combining jat the output of the optical module and forwarding

186, Network element 188 also connects to a network element 180 which includes a mobile switching center 184 and a home

af'fojrded by the present invention is defined by the appended claiijns .

Claims

2. A method_j according to claim 1, wherein the communication system fLs a cellular communication system, each sub- receiver being associated with a sub-cell of a cell associated with the receiver.

3 ^'. A method according to claim 2, wherein the identification of the sub-receiver at ,which a signal is received

I , j identifi s the ^;sub-cell area within which the signal is transmitted from.

4. A methcj according to blaim 3, further comprising identifying the I' location w Iithi .n ' the sub-cell from which the signal is transmitted from.

5. A methodi according to any one of claims 2 to 4 wherein the communication system is an indoor radio system.

A method according to any one of claims 1 to 6 wherein the signal is received from a mobile station.

7. A method according to any one of claims 1 to 6 wherein the

|ι receiver is part of a base transceiver station.

8. A receiver for receiving signals from a plurality of sub- receiverls, including: means for delaying a signal from ea <bh respective sub-receiver by a respective pre- determined time delay; and means for determining the presence l of a received signal in a time window associated with each respective time delay, wherein a signal received

wherein the delay element includes an optical transmission

I lirj .

13. A receiver according to any one of claims 8 to 12 wherein the means for determining the presence of a received signal includes a rake filter.

14. A receiver according to any one of claims 8 to 12 whdrein the receiver is associated with a base transceiver sts.tion defining a cell of the communication system, each s ¹ut -recei.1ver def'ining a sub'-cell' of the cell. 15 to claim 14, wherein a signal ^"at a particular sub-receiver e signal m the respective sub-

I 16. A receiver according to claim 15, further comprising means for identifying the location of the source of the signal in the sub-cell.